Devices for use in and on the human body are well known. The chemical composition of the surfaces of such devices plays a pivotal role in dictating the overall efficacy of the devices. For example, many devices, including catheters, stents, and implants require biologically non-fouling surfaces, meaning that proteins, lipids, and cells will not adhere to the surface. In some cases, materials for these devices are developed that are ideal in terms of strength, optimal transmission, flexibility and the like, but that foul when in use. In these cases, either new materials must be developed or an attempt to alter the surface characteristics of the materials must be made.
In the case of ophthalmic lenses, particularly contact lenses, many materials possess the desired oxygen permeability, mechanical and optical properties, yet are subject to rapid fouling. Additionally, the surface energies of the materials may be so low that the lenses are not sufficiently hydrophilic, meaning that they are not wettable by tear fluid. Contact lenses made of these materials can be uncomfortable to wear and may become tightly adhered to the cornea causing the potential for serious damage to the corneal epithelium.
A number of methods have been used to modify devices to improve their surface properties. For example, it is known to modify contact lenses made of silicone rubber polymers by grafting hydrophilic polymers onto the contact lens surface. However, such methods are disadvantageous in that they produce lenses with surfaces that are rough, uneven, or have pin-holes.
U.S. Pat. No. 4,332,922 discloses the conversion of silicone rubber lens surfaces to an oligomeric siloxane containing SiH groups and subsequently converting the SiH groups to SiOH groups or reacting the groups with C=C containing compounds to make the surface hydrophilic. However, the chemistry of this solution is limited.
Various methods using plasma techniques to coat hydrophobic substrates are known. However, all such plasma methods require that the substrates be exposed to vacuum, which is inconvenient and, at times, impracticable. Thus, a need exists for processes for modifying surface properties that overcome some of the disadvantages of the known processes.